After peripheral nerve damage, normal biochemical and morphological relationships between cell somata, their axonal and dendritic processes, and their terminations in targets such as muscle are disturbed both proximal and distal to the site of the injury. After a nerve is severed, the nerve end closest to the spinal cord normally begins to grow toward the other. The natural process of regeneration however is slow, and any number of things can obstruct or change the path of normal growth. One classical treatment for peripheral nerve repair requires "entubulization" of the severed nerve endings, a practice developed during World War II. In the practice of entubulization, empty plastic tubes are attached via microscopic sutures to the severed nerve endings; the tubes act as conduits to guide the growing nerve endings. Entubulization thus enhances the opportunity for some restitution of function, but unfortunately reverses only part of the damage. The restitution of function is rarely, if ever complete.
When a nerve link is broken the muscle which it serves begins to atrophy. The longer it takes for the nerve to regrow, the greater the damage to the muscle which it serves. Even after prosthetic implementation, considerable time is required and hence even after healing has begun, damage is sustained in the muscle served by the nerve. Consequently, the interaction of neuronal processes with the surfaces on which they grow has become a subject of increasing interest to neurobiologists interested in nerve regeneration. In vitro, it has been recognized that adhesion of growing processes, or neurites, to substrates is an important determinant of neurite elongation and that material deposited by non-neural cells can promote and direct neurite extension. regenerating peripheral axons frequently grow along basal laminae (connective tissue) to reach and reinnervate their targets. These observations led to the demonstration that laminin, a glycoprotein which is a structural component of adult basal laminae, can promote some neurite outgrowth. Although other molecular substances have been found useful in promoting neurite outgrowth, most attention has focussed on laminin. See Nature Vol. 315, June 27, 1985, Pages 714-715 "Laminin for axonal guidance" Joshua R. Sanes.